Expeditious Asymmetric Synthesis of Optically Pure δ-Lactones Bearing Consecutive Three Asymmetric Centers

The (4S)-isopropyl-1,3-thiazolidine-2-thione diamides of 3-substituted glutaric acids were submitted to enolization with Sn(CF3SO3)2 and N-ethylpiperidine. The resultant tin(II) enolate was treated with several aldehydes to give the aldols, which readily undergo basic lactonization affording the corresponding chiral δ-lactones bearing consecutive three asymmetric centers.